Linking Water Vapor Channels of GOES-11 and GOES-12 Imagers Using IASI Hyperspectral Observations

摘要

The potential use of the inter-calibration results to optimally integrate and merge data from GOES 11 and 12 imagers to create consistent, seamless global products is explored in this study. There are three steps involved, including 1) limb correction; 2) tying GOES measurements to IASI; and 3) resolving the SRF-difference-induced biases. We first use the IASI hyperspectral measurements on the polar-orbiting MetOp-A satellite to access the calibration accuracy of water vapor channels on the GOES-11 and GOES-12 imagers with one year of match-up data. The simultaneous nadir observations with homogeneous scenes from IASI and GOES imagers are spatially collocated. The IASI spectra are convolved with the GOES Imager SRFs to compare with GOES Imager observations. Assuming that IASI is well calibrated and can be used as a radiometric reference standard, the GOES imager water vapors were found to have an estimated calibration accuracy of less than 0.3 K (with a standard deviation of less than 0.2 K) at the BT range 240-260K relative to IASI, which meets the GOES imager design specification (1.0 K calibration accuracy for infrared channels). In a second step, merging GOES-11 and GOES-12 water vapor channel through IASI is investigated. A linear relationship is proposed. An example of creating water vapor composite image from the GOES-11 and GOES-12 to resolve their observational discrepancy is presented step-by-step. This study further demonstrates the usefulness of employing high spectral resolution radiance measurements to accurately assess broadband radiometer calibration and create the calibration link between instruments. In the future, we will extend this method to other satellites.